105 ideas
| 9535 | 'Contradictory' propositions always differ in truth-value [Lemmon] |
| Full Idea: Two propositions are 'contradictory' if they are never both true and never both false either, which means that ¬(A↔B) is a tautology. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9511 | We write the conditional 'if P (antecedent) then Q (consequent)' as P→Q [Lemmon] |
| Full Idea: We write 'if P then Q' as P→Q. This is called a 'conditional', with P as its 'antecedent', and Q as its 'consequent'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.2) | |
| A reaction: P→Q can also be written as ¬P∨Q. |
| 9510 | That proposition that either P or Q is their 'disjunction', written P∨Q [Lemmon] |
| Full Idea: If P and Q are any two propositions, the proposition that either P or Q is called the 'disjunction' of P and Q, and is written P∨Q. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.3) | |
| A reaction: This is inclusive-or (meaning 'P, or Q, or both'), and not exlusive-or (Boolean XOR), which means 'P, or Q, but not both'. The ∨ sign is sometimes called 'vel' (Latin). |
| 9509 | That proposition that both P and Q is their 'conjunction', written P∧Q [Lemmon] |
| Full Idea: If P and Q are any two propositions, the proposition that both P and Q is called the 'conjunction' of P and Q, and is written P∧Q. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.3) | |
| A reaction: [I use the more fashionable inverted-v '∧', rather than Lemmon's '&', which no longer seems to be used] P∧Q can also be defined as ¬(¬P∨¬Q) |
| 9508 | The sign |- may be read as 'therefore' [Lemmon] |
| Full Idea: I introduce the sign |- to mean 'we may validly conclude'. To call it the 'assertion sign' is misleading. It may conveniently be read as 'therefore'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.2) | |
| A reaction: [Actually no gap between the vertical and horizontal strokes of the sign] As well as meaning 'assertion', it may also mean 'it is a theorem that' (with no proof shown). |
| 9512 | We write the 'negation' of P (not-P) as ¬ [Lemmon] |
| Full Idea: We write 'not-P' as ¬P. This is called the 'negation' of P. The 'double negation' of P (not not-P) would be written as ¬¬P. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.2) | |
| A reaction: Lemmons use of -P is no longer in use for 'not'. A tilde sign (squiggle) is also used for 'not', but some interpreters give that a subtly different meaning (involving vagueness). The sign ¬ is sometimes called 'hook' or 'corner'. |
| 9513 | We write 'P if and only if Q' as P↔Q; it is also P iff Q, or (P→Q)∧(Q→P) [Lemmon] |
| Full Idea: We write 'P if and only if Q' as P↔Q. It is called the 'biconditional', often abbreviate in writing as 'iff'. It also says that P is both sufficient and necessary for Q, and may be written out in full as (P→Q)∧(Q→P). | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.4) | |
| A reaction: If this symbol is found in a sequence, the first move in a proof is to expand it to the full version. |
| 9514 | If A and B are 'interderivable' from one another we may write A -||- B [Lemmon] |
| Full Idea: If we say that A and B are 'interderivable' from one another (that is, A |- B and B |- A), then we may write A -||- B. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9516 | A 'well-formed formula' follows the rules for variables, ¬, →, ∧, ∨, and ↔ [Lemmon] |
| Full Idea: A 'well-formed formula' of the propositional calculus is a sequence of symbols which follows the rules for variables, ¬, →, ∧, ∨, and ↔. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.1) |
| 9517 | The 'scope' of a connective is the connective, the linked formulae, and the brackets [Lemmon] |
| Full Idea: The 'scope' of a connective in a certain formula is the formulae linked by the connective, together with the connective itself and the (theoretically) encircling brackets | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.1) |
| 9519 | A 'substitution-instance' is a wff formed by consistent replacing variables with wffs [Lemmon] |
| Full Idea: A 'substitution-instance' is a wff which results by replacing one or more variables throughout with the same wffs (the same wff replacing each variable). | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9529 | A wff is 'inconsistent' if all assignments to variables result in the value F [Lemmon] |
| Full Idea: If a well-formed formula of propositional calculus takes the value F for all possible assignments of truth-values to its variables, it is said to be 'inconsistent'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9531 | 'Contrary' propositions are never both true, so that ¬(A∧B) is a tautology [Lemmon] |
| Full Idea: If A and B are expressible in propositional calculus notation, they are 'contrary' if they are never both true, which may be tested by the truth-table for ¬(A∧B), which is a tautology if they are contrary. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9534 | Two propositions are 'equivalent' if they mirror one another's truth-value [Lemmon] |
| Full Idea: Two propositions are 'equivalent' if whenever A is true B is true, and whenever B is true A is true, in which case A↔B is a tautology. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9530 | A wff is 'contingent' if produces at least one T and at least one F [Lemmon] |
| Full Idea: If a well-formed formula of propositional calculus takes at least one T and at least one F for all the assignments of truth-values to its variables, it is said to be 'contingent'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9532 | 'Subcontrary' propositions are never both false, so that A∨B is a tautology [Lemmon] |
| Full Idea: If A and B are expressible in propositional calculus notation, they are 'subcontrary' if they are never both false, which may be tested by the truth-table for A∨B, which is a tautology if they are subcontrary. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9533 | A 'implies' B if B is true whenever A is true (so that A→B is tautologous) [Lemmon] |
| Full Idea: One proposition A 'implies' a proposition B if whenever A is true B is true (but not necessarily conversely), which is only the case if A→B is tautologous. Hence B 'is implied' by A. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9528 | A wff is a 'tautology' if all assignments to variables result in the value T [Lemmon] |
| Full Idea: If a well-formed formula of propositional calculus takes the value T for all possible assignments of truth-values to its variables, it is said to be a 'tautology'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.3) |
| 9518 | A 'theorem' is the conclusion of a provable sequent with zero assumptions [Lemmon] |
| Full Idea: A 'theorem' of logic is the conclusion of a provable sequent in which the number of assumptions is zero. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) | |
| A reaction: This is what Quine and others call a 'logical truth'. |
| 9398 | ∧I: Given A and B, we may derive A∧B [Lemmon] |
| Full Idea: And-Introduction (&I): Given A and B, we may derive A∧B as conclusion. This depends on their previous assumptions. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9397 | CP: Given a proof of B from A as assumption, we may derive A→B [Lemmon] |
| Full Idea: Conditional Proof (CP): Given a proof of B from A as assumption, we may derive A→B as conclusion, on the remaining assumptions (if any). | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9394 | MPP: Given A and A→B, we may derive B [Lemmon] |
| Full Idea: Modus Ponendo Ponens (MPP): Given A and A→B, we may derive B as a conclusion. B will rest on any assumptions that have been made. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9401 | ∨E: Derive C from A∨B, if C can be derived both from A and from B [Lemmon] |
| Full Idea: Or-Elimination (∨E): Given A∨B, we may derive C if it is proved from A as assumption and from B as assumption. This will also depend on prior assumptions. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9396 | DN: Given A, we may derive ¬¬A [Lemmon] |
| Full Idea: Double Negation (DN): Given A, we may derive ¬¬A as a conclusion, and vice versa. The conclusion depends on the assumptions of the premiss. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9393 | A: we may assume any proposition at any stage [Lemmon] |
| Full Idea: Assumptions (A): any proposition may be introduced at any stage of a proof. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9399 | ∧E: Given A∧B, we may derive either A or B separately [Lemmon] |
| Full Idea: And-Elimination (∧E): Given A∧B, we may derive either A or B separately. The conclusions will depend on the assumptions of the premiss. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9402 | RAA: If assuming A will prove B∧¬B, then derive ¬A [Lemmon] |
| Full Idea: Reduction ad Absurdum (RAA): Given a proof of B∧¬B from A as assumption, we may derive ¬A as conclusion, depending on the remaining assumptions (if any). | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9395 | MTT: Given ¬B and A→B, we derive ¬A [Lemmon] |
| Full Idea: Modus Tollendo Tollens (MTT): Given ¬B and A→B, we derive ¬A as a conclusion. ¬A depends on any assumptions that have been made | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9400 | ∨I: Given either A or B separately, we may derive A∨B [Lemmon] |
| Full Idea: Or-Introduction (∨I): Given either A or B separately, we may derive A∨B as conclusion. This depends on the assumption of the premisses. | |
| From: E.J. Lemmon (Beginning Logic [1965], 1.5) |
| 9521 | 'Modus tollendo ponens' (MTP) says ¬P, P ∨ Q |- Q [Lemmon] |
| Full Idea: 'Modus tollendo ponens' (MTP) says that if a disjunction holds and also the negation of one of its disjuncts, then the other disjunct holds. Thus ¬P, P ∨ Q |- Q may be introduced as a theorem. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) | |
| A reaction: Unlike Modus Ponens and Modus Tollens, this is a derived rule. |
| 9522 | 'Modus ponendo tollens' (MPT) says P, ¬(P ∧ Q) |- ¬Q [Lemmon] |
| Full Idea: 'Modus ponendo tollens' (MPT) says that if the negation of a conjunction holds and also one of its conjuncts, then the negation of the other conjunct holds. Thus P, ¬(P ∧ Q) |- ¬Q may be introduced as a theorem. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) | |
| A reaction: Unlike Modus Ponens and Modus Tollens, this is a derived rule. |
| 9525 | We can change conditionals into negated conjunctions with P→Q -||- ¬(P ∧ ¬Q) [Lemmon] |
| Full Idea: The proof that P→Q -||- ¬(P ∧ ¬Q) is useful for enabling us to change conditionals into negated conjunctions | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9524 | We can change conditionals into disjunctions with P→Q -||- ¬P ∨ Q [Lemmon] |
| Full Idea: The proof that P→Q -||- ¬P ∨ Q is useful for enabling us to change conditionals into disjunctions. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9523 | De Morgan's Laws make negated conjunctions/disjunctions into non-negated disjunctions/conjunctions [Lemmon] |
| Full Idea: The forms of De Morgan's Laws [P∨Q -||- ¬(¬P ∧ ¬Q); ¬(P∨Q) -||- ¬P ∧ ¬Q; ¬(P∧Q) -||- ¬P ∨ ¬Q); P∧Q -||- ¬(¬P∨¬Q)] transform negated conjunctions and disjunctions into non-negated disjunctions and conjunctions respectively. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9527 | The Distributive Laws can rearrange a pair of conjunctions or disjunctions [Lemmon] |
| Full Idea: The Distributive Laws say that P ∧ (Q∨R) -||- (P∧Q) ∨ (P∧R), and that P ∨ (Q∨R) -||- (P∨Q) ∧ (P∨R) | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9526 | We can change conjunctions into negated conditionals with P→Q -||- ¬(P → ¬Q) [Lemmon] |
| Full Idea: The proof that P∧Q -||- ¬(P → ¬Q) is useful for enabling us to change conjunctions into negated conditionals. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) |
| 9537 | Truth-tables are good for showing invalidity [Lemmon] |
| Full Idea: The truth-table approach enables us to show the invalidity of argument-patterns, as well as their validity. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.4) |
| 9538 | A truth-table test is entirely mechanical, but this won't work for more complex logic [Lemmon] |
| Full Idea: A truth-table test is entirely mechanical, ..and in propositional logic we can even generate proofs mechanically for tautological sequences, ..but this mechanical approach breaks down with predicate calculus, and proof-discovery is an imaginative process. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.5) |
| 9536 | If any of the nine rules of propositional logic are applied to tautologies, the result is a tautology [Lemmon] |
| Full Idea: If any application of the nine derivation rules of propositional logic is made on tautologous sequents, we have demonstrated that the result is always a tautologous sequent. Thus the system is consistent. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.4) | |
| A reaction: The term 'sound' tends to be used now, rather than 'consistent'. See Lemmon for the proofs of each of the nine rules. |
| 9539 | Propositional logic is complete, since all of its tautologous sequents are derivable [Lemmon] |
| Full Idea: A logical system is complete is all expressions of a specified kind are derivable in it. If we specify tautologous sequent-expressions, then propositional logic is complete, because we can show that all tautologous sequents are derivable. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.5) | |
| A reaction: [See Lemmon 2.5 for details of the proofs] |
| 13909 | Write '(∀x)(...)' to mean 'take any x: then...', and '(∃x)(...)' to mean 'there is an x such that....' [Lemmon] |
| Full Idea: Just as '(∀x)(...)' is to mean 'take any x: then....', so we write '(∃x)(...)' to mean 'there is an x such that....' | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.1) | |
| A reaction: [Actually Lemmon gives the universal quantifier symbol as '(x)', but the inverted A ('∀') seems to have replaced it these days] |
| 13902 | 'Gm' says m has property G, and 'Pmn' says m has relation P to n [Lemmon] |
| Full Idea: A predicate letter followed by one name expresses a property ('Gm'), and a predicate-letter followed by two names expresses a relation ('Pmn'). We could write 'Pmno' for a complex relation like betweenness. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.1) |
| 13911 | The 'symbols' are bracket, connective, term, variable, predicate letter, reverse-E [Lemmon] |
| Full Idea: I define a 'symbol' (of the predicate calculus) as either a bracket or a logical connective or a term or an individual variable or a predicate-letter or reverse-E (∃). | |
| From: E.J. Lemmon (Beginning Logic [1965], 4.1) |
| 13910 | Our notation uses 'predicate-letters' (for 'properties'), 'variables', 'proper names', 'connectives' and 'quantifiers' [Lemmon] |
| Full Idea: Quantifier-notation might be thus: first, render into sentences about 'properties', and use 'predicate-letters' for them; second, introduce 'variables'; third, introduce propositional logic 'connectives' and 'quantifiers'. Plus letters for 'proper names'. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.1) |
| 13904 | Universal Elimination (UE) lets us infer that an object has F, from all things having F [Lemmon] |
| Full Idea: Our rule of universal quantifier elimination (UE) lets us infer that any particular object has F from the premiss that all things have F. It is a natural extension of &E (and-elimination), as universal propositions generally affirm a complex conjunction. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.2) |
| 13906 | With finite named objects, we can generalise with &-Intro, but otherwise we need ∀-Intro [Lemmon] |
| Full Idea: If there are just three objects and each has F, then by an extension of &I we are sure everything has F. This is of no avail, however, if our universe is infinitely large or if not all objects have names. We need a new device, Universal Introduction, UI. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.2) |
| 13908 | UE all-to-one; UI one-to-all; EI arbitrary-to-one; EE proof-to-one [Lemmon] |
| Full Idea: Univ Elim UE - if everything is F, then something is F; Univ Intro UI - if an arbitrary thing is F, everything is F; Exist Intro EI - if an arbitrary thing is F, something is F; Exist Elim EE - if a proof needed an object, there is one. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.3) | |
| A reaction: [My summary of Lemmon's four main rules for predicate calculus] This is the natural deduction approach, of trying to present the logic entirely in terms of introduction and elimination rules. See Bostock on that. |
| 13901 | Predicate logic uses propositional connectives and variables, plus new introduction and elimination rules [Lemmon] |
| Full Idea: In predicate calculus we take over the propositional connectives and propositional variables - but we need additional rules for handling quantifiers: four rules, an introduction and elimination rule for the universal and existential quantifiers. | |
| From: E.J. Lemmon (Beginning Logic [1965]) | |
| A reaction: This is Lemmon's natural deduction approach (invented by Gentzen), which is largely built on introduction and elimination rules. |
| 13903 | Universal elimination if you start with the universal, introduction if you want to end with it [Lemmon] |
| Full Idea: The elimination rule for the universal quantifier concerns the use of a universal proposition as a premiss to establish some conclusion, whilst the introduction rule concerns what is required by way of a premiss for a universal proposition as conclusion. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.2) | |
| A reaction: So if you start with the universal, you need to eliminate it, and if you start without it you need to introduce it. |
| 13905 | If there is a finite domain and all objects have names, complex conjunctions can replace universal quantifiers [Lemmon] |
| Full Idea: If all objects in a given universe had names which we knew and there were only finitely many of them, then we could always replace a universal proposition about that universe by a complex conjunction. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.2) |
| 13900 | 'Some Frenchmen are generous' is rendered by (∃x)(Fx→Gx), and not with the conditional → [Lemmon] |
| Full Idea: It is a common mistake to render 'some Frenchmen are generous' by (∃x)(Fx→Gx) rather than the correct (∃x)(Fx&Gx). 'All Frenchmen are generous' is properly rendered by a conditional, and true if there are no Frenchmen. | |
| From: E.J. Lemmon (Beginning Logic [1965], 3.1) | |
| A reaction: The existential quantifier implies the existence of an x, but the universal quantifier does not. |
| 22246 | A train of reasoning must be treated as all happening simultaneously [Recanati] |
| Full Idea: For logic purposes, a train of reasoning has to be construed as synchronic. | |
| From: François Recanati (Mental Files in Flux [2016], 5.2) | |
| A reaction: If we are looking for a gulf between logic and the real world this is a factor to be considered, along with Nietzsche's observation about necessary simplification. [ref to Kaplan 'Afterthoughts' 1989, 584-5] |
| 9520 | The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q [Lemmon] |
| Full Idea: The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q. That is, since Napoleon was French, then if the moon is blue then Napoleon was French; and since Napoleon was not Chinese, then if Napoleon was Chinese, the moon is blue. | |
| From: E.J. Lemmon (Beginning Logic [1965], 2.2) | |
| A reaction: This is why the symbol → does not really mean the 'if...then' of ordinary English. Russell named it 'material implication' to show that it was a distinctively logical operator. |
| 16357 | Mental files are the counterparts of singular terms [Recanati] |
| Full Idea: Mental files are the mental counterparts of singular terms. | |
| From: François Recanati (Mental Files [2012], 3.3) | |
| A reaction: A thoroughly satisfactory theory. We can build up a picture of filing merging, duplication, ambiguity, error etc. Eventually neuroscience will map the whole system, and we will have cracked it. |
| 16360 | Identity statements are informative if they link separate mental files [Recanati] |
| Full Idea: An identity statement 'A=B' is informative to the extent that the terms 'A' and 'B' are associated with distinct mental files. | |
| From: François Recanati (Mental Files [2012], 4.1) | |
| A reaction: Hence the information in 'Scott is the author of 'Waverley'' is information about what is in your mind, not what is happening in Scotland. This is Recanati's solution to one of Frege's classic puzzles. 'Morning Star' and 'Evening Star' files. Nice. |
| 16374 | There is a continuum from acquaintance to description in knowledge, depending on the link [Recanati] |
| Full Idea: It is not too difficult to imagine a continuum of cases between straightforward instances of knowledge by acquaintance and straightforward instances of knowledge by description, with more or less tenuous informational links to the referent. | |
| From: François Recanati (Mental Files [2012], 12.2) |
| 7647 | The imagination alone perceives all objects; it is the soul, playing all its roles [La Mettrie] |
| Full Idea: The imagination alone perceives; it forms an idea of all objects, with the words and figures that characterise them; thus the imagination is the soul, because it plays all its roles. | |
| From: Julien Offray de La Mettrie (Machine Man [1747], p.15) | |
| A reaction: This is not just a big claim for the importance of imagination, in strong opposition to Descartes's rather dismissive view (Idea 1399), but also appears to be the germ of an interesting theory about the nature of personal identity. |
| 7645 | When falling asleep, the soul becomes paralysed and weak, just like the body [La Mettrie] |
| Full Idea: The soul and body fall asleep together. The soul slowly becomes paralysed, together with all the body's muscles. They can no longer hold up the weight of the head, while the soul can no longer bear the burden of thought. | |
| From: Julien Offray de La Mettrie (Machine Man [1747], p.6) | |
| A reaction: A very nice observation, to place alongside other evidence such as drunkenness and blushing. Personally I find it hard to see why anyone ever believed dualism. You don't need modern brain scans and brain lesion research to see the problem. |
| 23225 | The soul's faculties depend on the brain, and are simply the brain's organisation [La Mettrie] |
| Full Idea: All the soul's faculties depend so much on the specific organisation of the brain and of the whole body that they are clearly nothing but that organisation. | |
| From: Julien Offray de La Mettrie (Machine Man [1747], p.26) | |
| A reaction: An interesting idea because it suggests that La Mettrie is a functionalist, rather than simply a reductive physicalist. |
| 7652 | Man is a machine, and there exists only one substance, diversely modified [La Mettrie] |
| Full Idea: Let us conclude boldly that man is a machine and that there is in the whole universe only one diversely modified substance. | |
| From: Julien Offray de La Mettrie (Machine Man [1747], p.39) | |
| A reaction: What courage it must have taken to write what now seems a perfectly acceptable and normal view. One day there should be a collective monument to Hobbes, Gassendi, Spinoza, La Mettrie and Hume, who thought so boldly. |
| 7650 | All thought is feeling, and rationality is the sensitive soul contemplating reasoning [La Mettrie] |
| Full Idea: Thought is only a capacity to feel, and the rational soul is only the sensitive soul applied to the contemplation of ideas and to reasoning. | |
| From: Julien Offray de La Mettrie (Machine Man [1747], p.33) | |
| A reaction: What a very nice idea. La Mettrie wants to bring us closer to animals. Because we can pursue a train of rational thought, it does not follow that we have a faculty called 'rationality'. A dog can follow a clever series of clues that lead to food. |
| 18409 | Indexicals apply to singular thought, and mental files have essentially indexical features [Recanati] |
| Full Idea: I defend the applicability of the indexical model to singular thought, and to mental files qua vehicles of singular thought. Mental files, I will argue, possess the essential features of indexicals. | |
| From: François Recanati (Mental Files [2012], 05.1) | |
| A reaction: I love mental files, but am now (thanks to Cappelen and Dever) deeply averse to giving great significance to indexicals. A revised account of files will be needed. |
| 22247 | Indexicality is not just a feature of language; examples show it also occurs in thought [Recanati] |
| Full Idea: People once took indexicality to be exclusively a property of language, ....but a series of examples seemed to establish that the thought expressed by uttering an indexical sentence is itself indexical (and is thus 'essential'). | |
| From: François Recanati (Mental Files in Flux [2016], 6.1) | |
| A reaction: Perry's example of not realising it is him leaking the sugar in a supermarket is the best known example. Was this a key moment for realising that philosophy of thought is (pace Dummett) more important than philosophy of language? |
| 22248 | How can we communicate indexical thoughts to people not in the right context? [Recanati] |
| Full Idea: Indexical thoughts create an obvious problem with regard to communication. How can we manage to communicate such thoughts to those who are not in the right context? | |
| From: François Recanati (Mental Files in Flux [2016], 7.1) | |
| A reaction: One answer is that you often cannot communicate them. If I write on a wall 'I am here now', that doesn't tell the next passer-by very much. But 'it's raining here' said in a telephone call works fine - if you know the location of the caller. |
| 16354 | Indexicality is closely related to singularity, exploiting our direct relations with things [Recanati] |
| Full Idea: Singularity and indexicality are closely related: for indexicals systematically exploit the contextual relations in which we stand to what we talk about. | |
| From: François Recanati (Mental Files [2012], 2.2) | |
| A reaction: Recanati builds a nice case that we may only have an ontology of singular objects because we conceptualise and refer to things in a particular way. He denies the ontology, but that's the bit that interests me. |
| 16371 | Files can be confused, if two files correctly have a single name, or one file has two names [Recanati] |
| Full Idea: Paderewski cases are cases in which a subject associates two distinct files with a single name. Inverse Paderewski cases are cases in which there are two names but the subject associates them with a single file. | |
| From: François Recanati (Mental Files [2012], 10.1) | |
| A reaction: In the inverse there are two people with the same name, and someone thinks they are one person (with their combined virtues and vices). E.g. Einstein the famous physicist, and Einstein the famous musicologist. What a man! |
| 16373 | Encylopedic files have further epistemic links, beyond the basic one [Recanati] |
| Full Idea: The reference of a file is the object to which the subject stands in the relevant epistemic relation. In the case of encylopedic entries there is an arbitrary number of distinct relations. The file grows new links in an opportunistic manner. | |
| From: François Recanati (Mental Files [2012], 11.3) | |
| A reaction: I'm not convinced by Recanati's claim that encylopedic files are a distinct type. My files seem to grow these opportunistic links right from their inception. All files seem to have that feature. A file could have four links at its moment of launching. |
| 16375 | Singular thoughts need a mental file, and an acquaintance relation from file to object [Recanati] |
| Full Idea: The mental file framework rests on two principles: that the subject cannot entertain a singular thought about an object without possessing and exercising a mental file about it, and that this requires an acquaintance relation with the object. | |
| From: François Recanati (Mental Files [2012], 12.3) | |
| A reaction: I'm puzzled by the case where I design and build a completely new object. I seem to assemble a file, and only bestow singularity on it towards the end. Or the singularity can just be a placeholder, referred to as 'something'. […see p.158] |
| 16377 | Expected acquaintance can create a thought-vehicle file, but without singular content [Recanati] |
| Full Idea: On my view, actual acquaintance is not necessary to open a mental file; expected acquaintance will suffice; yet opening a mental file itself is not sufficient to entertain a singular thought-content. It only enables a thought-vehicle. | |
| From: François Recanati (Mental Files [2012], 13.1) | |
| A reaction: I'm not clear why I can't create a file with no expectation at all of acquaintance, as in a fictional case. Depends what 'acquaintance' means. Recanati longs for precise distinctions where they may not be available. |
| 16378 | An 'indexed' file marks a file which simulates the mental file of some other person [Recanati] |
| Full Idea: Files function metarepresentationally if they serve to represent how other subjects think about objects in the world. ..An 'indexed' file has an index referring to the other subject whose files the indexed file stands for or simulates. | |
| From: François Recanati (Mental Files [2012], 14.1) | |
| A reaction: Presumably there is an implicit index on all files, which says in a conversation whether my interlocutor does or does not hold the same file-type as me. Recanati wants many 'types' of files, but I suspect there is just one file type. |
| 16387 | Reference by mental files is Millian, in emphasising acquaintance, rather than satisfaction [Recanati] |
| Full Idea: The mental file account preserves the original, Millian inspiration of direct reference theories in giving pride of place to acquaintance relations and downplaying satisfaction factors. | |
| From: François Recanati (Mental Files [2012], 17.3) | |
| A reaction: I find this a very satisfying picture, in which reference links to the simple label of a file (which could be a number), and not to its contents. There are tricky cases of non-existents, fictional entities and purely possible entities to consider. |
| 16358 | The reference of a file is fixed by what it relates to, not the information it contains [Recanati] |
| Full Idea: What files refer to is not determined by properties which the subject takes the referent to have (information, or misinformation, in the file), but through the relations on which the files are based. | |
| From: François Recanati (Mental Files [2012], 3.3) | |
| A reaction: Maybe. 'Lot 22'. I can build up a hypothetical file by saying 'Imagine an animal which is F, G, H…', and build a reference that relates to nothing. Maybe Recanati overestimates the role of his 'epistemically rewarding' relations in file creation. |
| 16361 | A mental file treats all of its contents as concerning one object [Recanati] |
| Full Idea: The role of a mental file is precisely to treat all the information as if it concerned one and the same object, from which it derives. | |
| From: François Recanati (Mental Files [2012], 4.1) | |
| A reaction: Recanati's book focuses entirely on singular objects, but we presumably have files for properties, generalisation, groups etc. Can they only be thought about if they are reified? Maybe. |
| 16367 | There are transient 'demonstrative' files, habitual 'recognitional' files, cumulative 'encyclopedic' files [Recanati] |
| Full Idea: A 'demonstrative' file only exists during the demonstrative relation to something; …a 'recognitional' file is based on 'familiarity' (a disposition to recognise); …an 'encylopedic' file contains all the information on something, however it is gained. | |
| From: François Recanati (Mental Files [2012], 6.1-3) | |
| A reaction: [picked as samples of his taxonomy, pp.70-73] I'm OK with this as long as he doesn't think the categories are sharply separated. I'm inclined to think of files as a single type, drifting in and out of different of modes. |
| 16368 | Files are hierarchical: proto-files, then first-order, then higher-order encyclopedic [Recanati] |
| Full Idea: There is a hierarchy of files. Proto-files are the most basic; conceptual files are generated from them. First-order ones are more basic, as the higher-order encylopedic entries presuppose them. | |
| From: François Recanati (Mental Files [2012], 6.3) | |
| A reaction: This hierarchy might fit into a decent account of categories, if a plausible one could be found. A good prospect for exploring categories would be to start with mental file-types, and work outwards through their relations. |
| 16370 | A file has a 'nucleus' through its relation to the object, and a 'periphery' of links to other files [Recanati] |
| Full Idea: I take a file to have a dual structure, with a 'nucleus' of the file consisting of information derived through the relevant epistemically rewarding relation, while the 'periphery' consists of information derived through linking with other files. | |
| From: François Recanati (Mental Files [2012], 8.3) | |
| A reaction: This sounds strikingly like essentialism to me, though what constitutes the essence is different from the usual explanatory basics. The link, though, is in the causal connection. If we naturally 'essentialise', that will control file-formation. |
| 22242 | Mental files are concepts, which are either collections or (better) containers [Recanati] |
| Full Idea: Mental files are entries in the mental encyclopedia, that is, concepts. Some, following Grice, say they are information collections, but I think of them as containers. Collections are determined by their elements, but containers have independent identity. | |
| From: François Recanati (Mental Files in Flux [2016], Pref) | |
| A reaction: [compressed] [Grice reference is 'Vacuous Names' (1969)] I agree with Recanati. The point is that you can invoke a file by a label, even when you don't know what the content is. |
| 22243 | The Frege case of believing a thing is both F and not-F is explained by separate mental files [Recanati] |
| Full Idea: Frege's Constraint says if a subject believes an object is both F and not-F (as in 'Frege cases'), then the subject thinks of that object under distinct modes of presentation. Having distinct mental files of the object is sufficient to generate this. | |
| From: François Recanati (Mental Files in Flux [2016], Pref) | |
| A reaction: [compressed] When you look at how many semantic puzzles (notably from Frege and Kripke) are solved by the existence of labelled mental files, the case for them is overwhelming. |
| 7651 | With wonderful new machines being made, a speaking machine no longer seems impossible [La Mettrie] |
| Full Idea: If wonderful machines like Huygens's planetary clock can be made, it would take even more cogs and springs to make a speaking machine, which can no longer be considered impossible, particularly at the hands of a new Prometheus. | |
| From: Julien Offray de La Mettrie (Machine Man [1747], p.34) | |
| A reaction: Compare Descartes in Idea 3614. The idea of artificial intelligence does not arise with the advent of computers; it follows naturally from the materialist view of the mind, along with a bit of ambition to build complex machines. |
| 16381 | The content of thought is what is required to understand it (which involves hearers) [Recanati] |
| Full Idea: As Evans emphasises, what matters when we want to individuate semantic content is what would count as a proper understanding of an utterance; but 'understanding' defines the task of the hearer. | |
| From: François Recanati (Mental Files [2012], 16.2) | |
| A reaction: [cites Evans 1982: 92, 143n, 171] I like to place (following Aristotle) understanding at the centre of all of philosophy, so this seems to me an appealing idea. It makes misunderstandings interesting. |
| 16365 | Mental files are individual concepts (thought constituents) [Recanati] |
| Full Idea: I want mental files (properly speaking) to serve as individual concepts, i.e. thought constituents. | |
| From: François Recanati (Mental Files [2012], 5.3) | |
| A reaction: This is why the concept of mental files is so neat - it gives you a theory of reference and a theory of concepts. I love the files approach because it precisely fits my own introspective experiences. Hope I'm not odd in that way. |
| 16356 | There may be two types of reference in language and thought: descriptive and direct [Recanati] |
| Full Idea: A widely held view, originating with Russell, says there are two types of reference (both in language and thought): descriptive reference, and direct reference. | |
| From: François Recanati (Mental Files [2012], 3.2) | |
| A reaction: I would rather say is there is just one sort of reference, and as many ways of achieving it as you care to come up with. With that view, most of the problems vanish, as far as I can see. People refer. Sentences are nothing but trouble. |
| 16393 | In super-direct reference, the referent serves as its own vehicle of reference [Recanati] |
| Full Idea: In super-direct reference, the sort of thing Russell was after, there is no mode of presentation: the referent itself serves as its own vehicle, as it were. | |
| From: François Recanati (Mental Files [2012], 18.2) | |
| A reaction: To me this is a step too far, because reference is not some physical object like a chair; it is a mental or linguistic phenomenon. Chair's don't refer themselves; it is people who refer. |
| 16386 | Direct reference is strong Millian (just a tag) or weak Kaplanian (allowing descriptions as well) [Recanati] |
| Full Idea: There are two notions of direct reference, the strong Millian notion (where the expression is like a 'tag' with no satisfaction mechanism), and the weaker Kaplanian notion (where reference is compatible with carrying a descriptive meaning). | |
| From: François Recanati (Mental Files [2012], 17.3) | |
| A reaction: I immediately favour the Millian view, which gives a minimal basis for reference, as just a 'peg' (Marcus) to hang things on. I don't take a Millian reference to be the object itself. The concept of a 'tag' or 'label' is key. Mental files have tags. |
| 16372 | Sense determines reference says same sense/same reference; new reference means new sense [Recanati] |
| Full Idea: To say that sense determines reference is to say that the same sense cannot determine distinct referents - any distinction at the level of reference entails a corresponding distinction at the level of sense. | |
| From: François Recanati (Mental Files [2012], 10.2) | |
| A reaction: Does 'the sentry at the gate' change its sense when the guard is changed? Yes. 'The sentry at the gate will stop you'. 'The sentry at the gate is my cousin'. De re/de dicto reference. So changes of de re reference seem to change the sense? |
| 16388 | We need sense as well as reference, but in a non-descriptive form, and mental files do that [Recanati] |
| Full Idea: My view inherits from Frege 'modes of presentation'. Reference is not enough, and sense is needed. …We must make room for non-descriptive modes of presentation, and these are mental files. | |
| From: François Recanati (Mental Files [2012], 18.1) | |
| A reaction: [compressed] Recanati aims to avoid the standard Kripkean criticisms of descriptivism, while being able to handle Frege's puzzles. I take Recanati's mental files theory to be the most promising approach. |
| 16359 | Sense is a mental file (not its contents); similar files for Cicero and Tully are two senses [Recanati] |
| Full Idea: What plays the role of sense is not information in a file, but the file itself. If there are two distinct files, one for 'Cicero' and one for 'Tully', then there are two distinct (non-descriptive) senses, even if the information in both files is the same. | |
| From: François Recanati (Mental Files [2012], 3.4) | |
| A reaction: This may be the best idea in Recanati's book. A sense might be a 'way of coming at the information', rather than some set of descriptions. |
| 16355 | Problems with descriptivism are reference by perception, by communications and by indexicals [Recanati] |
| Full Idea: Three problems with Frege's idea of descriptions in the head are: reference through perception, reference through communicative chains, and reference through indexicals. | |
| From: François Recanati (Mental Files [2012], 3.1) | |
| A reaction: In the end reference has to occur in the head, even if it is social or causal or whatever, so these are not problems that worry me. |
| 16348 | Descriptivism says we mentally relate to objects through their properties [Recanati] |
| Full Idea: Descriptivism is the view that our mental relation to individual objects goes through properties of those objects. …This is so because our knowledge of objects is mediated by our knowledge of their properties. | |
| From: François Recanati (Mental Files [2012], 1.1) | |
| A reaction: The implication is that if you view an object as just a bundle of properties, then you are obliged to hold a descriptive theory of reference. Hence a 'singularist' theory of reference seems to need a primitive notion of an object's identity. |
| 16384 | Definite descriptions reveal either a predicate (attributive use) or the file it belongs in (referential) [Recanati] |
| Full Idea: A definite description may contribute either the singular predicate it encodes (attributive use) or the mental file to what that predicate belongs (referential use). | |
| From: François Recanati (Mental Files [2012], 17.1) | |
| A reaction: This nicely explains Donnellan's distinction in terms of mental files. 'Green' may refer in a shop, but isn't much use in a wood. What to make of 'He's a bit of a Bismark'? |
| 16352 | A rigid definite description can be attributive, not referential: 'the actual F, whoever he is….' [Recanati] |
| Full Idea: A rigid use of a definite description need not be referential: it may be attributive. Thus I may say: 'The actual F, whoever he is, is G'. | |
| From: François Recanati (Mental Files [2012], 2.2) | |
| A reaction: Recanati offers this as a criticism of the attempted 2-D solution to descriptivist accounts of singularity. The singularity is not strong enough, he says. |
| 22245 | A linguistic expression refers to what its associated mental file refers to [Recanati] |
| Full Idea: Mental files determine the reference of linguistic expressions: an expression refers to what the mental file associated with it refers to (at the time of tokening). | |
| From: François Recanati (Mental Files in Flux [2016], 5) | |
| A reaction: Invites the question of how mental files manage to refer, prior to the arrival of a linguistic expression. A mental file is usually fully of descriptions, but it might be no more than a label. |
| 16353 | Singularity cannot be described, and it needs actual world relations [Recanati] |
| Full Idea: As Peirce insisted, singularity as such cannot be described, it can only be given through actual world relations. | |
| From: François Recanati (Mental Files [2012], 2.2) | |
| A reaction: [Peirce - Exact Logic, Papers 3, 1967, §419] This is the key idea for Recanati's case for basing our grasp of singular things on their relation to a mental file. |
| 16382 | Fregean modes of presentation can be understood as mental files [Recanati] |
| Full Idea: A mental file plays the role which Fregean theory assigns to modes of presentation. | |
| From: François Recanati (Mental Files [2012], 17.1) | |
| A reaction: I'm a fan of mental files, and this is a nice pointer to how the useful Fregean insights can be written in a way better grounded in brain operations. Rewriting Frege in neuroscience terms is a nice project for someone. |
| 16389 | If two people think 'I am tired', they think the same thing, and they think different things [Recanati] |
| Full Idea: If you and I think 'I am tired', there is a sense in which we think the same thing, and another sense in which we think different things. | |
| From: François Recanati (Mental Files [2012], 18.1) | |
| A reaction: This is a very nice simple account of the semantic distinctiveness of indexicals, which obviously requires a 'two-tiered framework'. He cites Kaplan and Perry as background. |
| 16363 | Indexicals (like mental files) determine their reference relationally, not by satisfaction [Recanati] |
| Full Idea: The class of indexicals have the same property as mental files, that their reference is determined relationally rather than satisfactionally. | |
| From: François Recanati (Mental Files [2012], 5.1) | |
| A reaction: Recanati is building an account of reference through mental files. This idea may be the clearest point I have yet encountered about indexicals, showing why they are of particular interest to philosophers. |
| 16364 | Indexical don't refer; only their tokens do [Recanati] |
| Full Idea: Indexicals do not refer; only tokens of an indexical refer | |
| From: François Recanati (Mental Files [2012], 5.1) | |
| A reaction: Thus 'Thurs 23rd March 2013' refers, but 'now' doesn't, unless someone produces an utterance of it. This is why indexicals are sometimes called 'token-reflexives'. |
| 16351 | In 2-D semantics, reference is determined, then singularity by the truth of a predication [Recanati] |
| Full Idea: In the two-dimensional framework, what characterises the singular case is the fact that truth-evaluation (of possessing of the reference-fixing property) takes place at a later stage than reference determination. | |
| From: François Recanati (Mental Files [2012], 2.1) | |
| A reaction: This sounds psychologically plausible, which is a big (and unfashionable) plus for me. 1) what are we talking about? 2) what are we saying about it, 3) is it true? |
| 16350 | Two-D semantics is said to help descriptivism of reference deal with singular objects [Recanati] |
| Full Idea: Descriptivism has trouble catching the singularity of objects, construing them as only directly about properties. …To get the truth-conditions right, it is claimed, the descriptivist only as to go two-dimensional. | |
| From: François Recanati (Mental Files [2012], 2.1) | |
| A reaction: I suspect that the descriptivist only has a problem here because context is being ignored. 'That man on the beach' can quickly be made uniquely singular after a brief chat. |
| 16380 | Russellian propositions are better than Fregean thoughts, by being constant through communication [Recanati] |
| Full Idea: The Russellian notion of a proposition is arguably a better candidate for the status of semantic content than the Fregean notion of a thought. For the proposition remains constant from one person to the next. | |
| From: François Recanati (Mental Files [2012], 16.2) | |
| A reaction: A good point, though I rebel against Russellian propositions because they are too much out in the world, and propositions strike me as features of minds. We need to keep propositions separate from facts. |
| 22250 | There are speakers' thoughts and hearers' thoughts, but no further thought attached to the utterance [Recanati] |
| Full Idea: There is the speaker's thought and the thought formed by the hearer. That is all there is. We don't need an additional entity, the thought expressed by the utterance. | |
| From: François Recanati (Mental Files in Flux [2016], 7.2) | |
| A reaction: This fits my view of propositions nicely. They are the two 'thoughts'. The notion of some further abstract 'proposition' with its own mode of independent existence strikes me as ontologically absurd. |
| 22249 | The Naive view of communication is that hearers acquire exactly the thoughts of the speaker [Recanati] |
| Full Idea: The Naive Conception of Communication rests on the idea that communication is the replication of thoughts: the thought the hearer entertains when he understands what the speaker is saying is the very thought which the speaker expressed. | |
| From: François Recanati (Mental Files in Flux [2016], 7.1) | |
| A reaction: It is hard to believe that any modern thinker would believe such a view, given holistic views of language etc. |
| 7648 | The sun and rain weren't made for us; they sometimes burn us, or spoil our seeds [La Mettrie] |
| Full Idea: The sun was not made in order to heat the earth and all its inhabitants - whom it sometimes burns - any more than the rain was created in order to grow seeds - which it often spoils. | |
| From: Julien Offray de La Mettrie (Machine Man [1747]) | |
| A reaction: This denial of Aristotelian (and divine) teleology is as much part of the movement against religion, as are concerns about natural evil, and about the weakness of arguments for God's existence. These facts were obvious long before La Mettrie. |
| 7646 | There is no abrupt transition from man to animal; only language has opened a gap [La Mettrie] |
| Full Idea: From animals to man there is no abrupt transition. What was man before he invented words and learnt languages? An animal of a particular species, with much less natural instinct than the others. | |
| From: Julien Offray de La Mettrie (Machine Man [1747], p.13) | |
| A reaction: This shows how strongly the evolutionary idea was in the air, a century before Darwin proposed a mechanism for it. This thought is the beginning of a very new view of man, and also of a very new view of animals. |
| 7649 | There is no clear idea of the soul, which should only refer to our thinking part [La Mettrie] |
| Full Idea: The soul is merely a vain term of which we have no idea and which a good mind should use only to refer to that part of us which thinks. | |
| From: Julien Offray de La Mettrie (Machine Man [1747]) | |
| A reaction: I have always found the concept of the soul particularly baffling. It seems that it is only believed in to make immortality possible, with no other purpose to the belief, let alone evidence. I suspect that Descartes agreed with La Mettrie on this. |